Conventional thermoelectric devices such as thermoelectric generating devices or Peltier cooling devices can be fabricated by forming thermocouples from rigid thermoelectric materials such as bismuth-tellurium and disposing a large number of such thermocouples in parallel in the direction of the heat flow. Usually, the thermoelectric material is a bulk material having a columnar shape with a diameter of several millimeters (mm) or a rectangular shape having one side with a length of several mm. In such devices, the cross-section (which is circular, square, or low oblateness rectangular) is directed perpendicular to the heat flow direction. Recently, attempts have been made to produce such thermoelectric devices using thin film thermoelectric materials.
Thermoelectric devices generate power by having a temperature difference between a hot junction and a cold junction. One method of improving the efficiency therefore is to reduce the heat conducted from the hot junction to the cold junction as much as possible and to create a larger temperature difference between the two junctions. However, in conventional thermoelectric devices, the amount of heat released from the thermoelectric material surface is not sufficiently affected. Furthermore, it is sometimes difficult to maintain a large enough temperature difference between the two junctions.
Japanese Unexamined Patent Publication No. 2003-133600 describes a thermoelectric conversion member that converts heat into electricity by utilizing a temperature difference. The device includes two thin-film thermoelectric device layers, one having a p-type semiconductor and one having an n-type semiconductor. The layers are formed by vapor deposition on a flexible substrate.
Thin film thermoelectric materials can have increased heat release from the surface because of the relative increase in the surface area exposed to the outside. However, since the thermal conductivity of generally used inorganic thermoelectric materials are high (for example, from 1.5 to 2.0 W/(m·K) for a Bi—Te alloy (see, J. P. Fleurial et al., J. Phys. Chem. Solids, 49, 1237 (1988)) and 4 W/(m·K) for an Si—Ge alloy (see, Netsuden Henkan Zairyo (Thermoelectric Conversion Material), Nikkan Kogyo Sha (2005)), a sufficiently large temperature difference between the two junctions often cannot be maintained due to heat transfer from the hot junction to the cold junction.
Even though it has low electrical conductivity (about 200 S/cm), polyaniline is widely used in anti-electrostatic applications because of the ease in handling and processing the polymer. Increasing its electrical conductivity could enhance its usage, for example in thermoelectric devices. One method of increasing its electrical conductivity is by combining it with metal nanoparticles.
Japanese Unexamined Patent Publication No. 2004-359742 describes a noble metal-based catalyst-supported electrically conductive composite material produced by performing a polymerization reaction of an electrically conductive polymer using a noble metal complex as an oxidizing agent. The polymerization simultaneously loads the noble metal-based complex into the polymer while reducing the noble metal-based catalyst.
Japanese Unexamined Patent Publication No. 2006-248959 discloses a π-conjugated molecular compound-metal nanocluster that includes a π-conjugated molecular compound with metal or metal oxide fine particles dispersed therein. The nanoclusters are produced by mixing a metal salt and a π-conjugated molecular compound in a solvent and adding sodium borohydride as a reducing agent.
There still remains a need for electrically conductive polymers that include metal nanoparticles having higher electrical conductivities and increased compatibility and/or ease of dispersion of the metal nanoparticle.